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Fig. 5. Cell stretching images and analyzed data associated with the stretched length. (a) The images indicate that the stretching test is carried out at various volt- age inputs to the transducer; 16 Vpp ((b) Temporal displacement change at the indi- cated voltage.
The membrane properties of cancer cells were also stud- ied with an acoustic beam with the similar method17. The 5μm fibronectin-coated microbead was trapped in a 200 MHz acoustic trap and successfully attached to the mem- brane of a single breast cancer cell (MCF-7). The fibronectin proteins here allowed the microbead to be firmly attached to cell membrane. The cell membrane was then stretched by trapping the microbead in the acoustic beam. Fig. 5 shows that the cell membrane is stretched through the trapped microbead when the transducer is on. The stretched distance of the cell membrane was found to be ~4.7 μm at the input voltage of 16 Vpp.
Looking Ahead
Although optical tweezers have the advantages in resolu- tion and accurate control of smaller particles, i.e., nanoparti- cles, the direct exposure of cells to the optical tapping laser beam may cause changes in cellular properties. Those disad- vantages may place severe limits in the application of this technology. Acoustic tweezers that do not have these prob- lems may serve as an alternative to optical tweezers in many of these studies. Biomedical applications including measur- ing white cell adhesive forces are being explored in the NIH TRC at the University of Southern California.AT
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